Evaluation of Water Quality Indices: Use, Evolution and Future Perspectives

Abstract

The evaluation of the quality of water bodies is of fundamental importance to the study and use of water. Aiming to improve the understanding of the phenomena which occur in these environments, several indices have been proposed over the years, using several statistical, mathematical and computational techniques. For this, it is necessary to know the variables which influence different water bodies. However, not all places are able to make the most diverse analyses due to the financial and sanitary conditions, which can promote greater expenses in treatment as well as make the limits of tolerance of the water quality higher. Nowadays, there is a need to formulate indices which can address climate change in its variables, making it even closer to reality. In this context, seeking to reduce the number of variables used, collection costs, laboratory analyses and a greater representativeness of the indices, multivariate statistical techniques and artificial intelligence are being increasingly used and obtaining expressive results. These advances contribute to the improvement of water quality indices, thus seeking to obtain one which portrays the various phenomena which occur in water bodies in a more rapid and coherent way with the reality and social context of water resources.

New Water and Biotic Quality Assessment Indices for a tropical reservoir based on fuzzy logic

“…This index was specifically designed for public water supply and incorporates nine variables considered relevant for water quality evaluations. Recently, Garcia et al (2018) presented a review of water quality indices, discussing their evolution and future perspectives.…”

Functional quality of urban surface water

“…We define four classes for the sub-index scores per parameter and the overall SI score, ranging from low suitability (score=1) to excellent suitability (score=4). This approach is in line with the rationale behind almost all WQIs, where scores are positively related to water quality and the number of water quality classes usually varies between four and six (Borges Garcia et al, 2018;Lumb et al, 2011) If there are conditions in which it is physically impossible to use the water for the specific use function, a precondition is defined for the parameter(s) that impede the use. If the precondition is not met, the water is considered unsuitable and the assigned SI score is 0.…”

“…A WQI describes water quality with a single value and is based on the integration of sub-scores for relevant parameters. The advantages of the WQI model are that an index is simple and easy to understand by a broad audience (Borges Garcia et al, 2018;Lumb et al, 2011;Sarkar & Majumder, 2020), requires a modest amount of input data, and an integrated index provides more information than a single water quality parameter (Azevedo .…”

“…WQIs however cannot be used to review functional quality of urban surface water for the full range of single use functions. WQIs are mainly targeted at ecological water quality and/or suitability of water for drinking water production and irrigation (Alvareda et al, 2020;Borges Garcia et al, 2018;Lumb et al, 2011). Because of this focus, WQIs typically classify water quality as grade of pollution or purity.…”

“…The basic concept is that a selection of relevant parameters is rated and the scores are integrated into a composite index. Advantages of the use of WQIs are that they are simple (Borges Garcia et al, 2018;Lumb et al, 2011;Sarkar & Majumder, 2020), requiring a modest amount of input data, and understandable for a broad audience of non-specialists (Azevedo . A composite index is also considered to provide a more accurate reflection of water quality compared to a review of single water quality parameters (Noori et al, 2019).…”